This application claims the priority of Korean Patent Application No. 10-2003-0065570 filed on Sep. 22, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of Invention
The present invention relates to a service search system and method for a wireless ad hoc network, and more particularly, to an efficient service searching system and method for a wireless ad hoc network, which enables efficient searches of services due to reduction in load by preventing unnecessary broadcasts in a wireless ad hoc network environment.
2. Description of the Prior Art
A typical service search system for a wired network environment, as shown in FIG. 1, comprises a user agent 10 requesting a desired service, a service agent 20 for providing the service requested by the user agent 10, a directory agent 30 for storing information on the service agent 20 therein and sending the information on the service agent 20 upon reception of a service request from the user agent 10, and a dynamic host configuration protocol (DHCP) 40 for providing the address of the directory agent 30 to the user agent 10.
Further, the user agent 10, the service agent 20, the directory agent 30 and the DHCP 40 are connected to one another via a given wired network 50.
At this time, the service agent information includes the service content, IP address and the like of a service agent providing a relevant service.
Further, the directory agent 30 may be eliminated, if necessary. If there is no directory agent 30, the user agent 10 broadcasts a service request packet and then uses a relevant service through a response sent by the service agent 20 in response to the service request packet.
The operation of the service searching system varies depending on the existence or absence of the directory agent 30. First, a case where there is no directory agent 30 will be discussed. The user agent 10 broadcasts a service request packet through the wired network.
In a case where the service agent 20 that has received the service request packet provides the requested service, the service agent 20 issues a service response in a unicast manner by which a relevant response signal is sent directly to the user agent 10.
Meanwhile, if there is a directory agent 30, the service agent 20 first registers providable services with the directory agent 30.
Thereafter, the user agent 10 finds out the address of the directory agent 30 through the DHCP 40 and requests a desired service.
If there is a service agent 20 capable of providing a service corresponding to the request, the directory agent 30 provides the address of the relevant service agent 20.
If a service agent 20 capable of providing the relevant service does not exist in the directory agent 30, the user agent 10 broadcasts a service request packet.
Meanwhile, as the utility of wireless networks has been recently highlighted, studies have been conducted on service search methods for wireless networks.
As a result, there have been attempts to apply a service, search method for wired networks to wireless networks.
However, since the aforementioned service search system and method have been developed based on a wired network, it causes routing problems in a wireless ad hoc network environment in which respective terminals serve as routers in that the respective terminals should be searched every broadcast and thus a heavy load is exerted on the entire wireless ad hoc network.
Meanwhile, there is a problem with the selection of the directory agent 30 to employ the directory agent in the wireless ad hoc network.
That is, a predetermined selection algorithm should be used to select the directory agent, and as part of this process, a heavy load is caused due to the participation of all terminals in the network.
Moreover, there is a problem in that the efficiency of a terminal selected as a directory agent is degraded since much power and bandwidth is used for service search in the terminal.
There is another problem in that if the terminal selected as the directory agent deviates from radio wave coverage or the supply of power thereto is turned off, it cannot be used and thus a directory agent needs to be selected again, thereby causing heavy load on the network.